Ultrasonic guided wave techniques are utilized in a wide range of non-destructive inspection applications including those for pipes, plates, and shells comprised of metals, composites, and other materials. Guided waves are elastic waves propagating in a bounded structure that is utilized as a waveguide to efficiently transmit one or more wave modes along the structure. One of the foremost benefits of guided waves over other non-destructive inspection techniques is the ability of said waves to propagate over long distances, in many cases hundreds of feet, and to inspect inaccessible or hidden structures from a single probe position.
Long-range guided wave techniques are often utilized for the inspection of pipelines, plates, and shells. However, due to the nature of the guided waves and associated electronics used in such applications, there are inherent limitations of this technology. Two of these limitations are the existence of an uninspectable region, i.e. ‘dead zone’, around the transducer and a lack of axial and lateral resolution in many applications. Due to these limitations, guided waves are often used as a screening tool for large sections of a structure. However, there exist many opportunities for guided wave applications over short and medium ranges that require greater axial and lateral resolution. Several examples of these opportunities include the detection of corrosion, cracks, and other flaws in close proximity to structural features such as supports, welds, flanges, and air-soil interfaces as well as inspection of short, inaccessible regions such as corrosion under pipe supports (CUPS). The disclosed magnetostrictive ultrasonic guided wave scanner system advantageously yields two-dimensional scan images featuring improved axial and lateral resolution and featuring a small dead zone compared to conventional guided wave inspection systems.